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Post by podpilot on Apr 11, 2020 19:25:46 GMT
Aircraft: Tecnam Astore N715RW, 2015, Serial #43 Flight 4/10/20
I was twenty miles south of destination, ATW, descending from 7500' cruising altitude, throttled back. Smelled smoke in cockpit. One-two minutes later, smoke was visible. Turned off cabin heat, turned on vents. Smoke cleared. Began to lose power. Oil pressure began to decline. Cylinder head temp, oil temp, fuel pressure, manifold pressure remained in green. Circuit breakers all normal. On two mile base leg, oil pressure was in the red, indicating 20-22 on the gauge. Declared an emergency. Landed uneventfully. Tower reported smoke emanating from rear of plane.
Plane had oil change about five hours previous.
At maintenance shop on field, pulled off cowlings. Oil filter was tight. No evidence of leak there or at quick drain. Few drops of sticky black oil on lower left cowling aft of filter. Not sure whether these were new or left from oil change.
Scorching forward and about the turbo which is located immediately adjacent to exhaust housing cuff for cabin heat. Not certain whether this a cause or effect of failure. Turbo fan spun freely.
About a pint of oil was drained from oil reservoir. Belly of plane showed some staining consistent with smoke but not liquid oil.
Below should be a ink to photographs taken of the plane, engine, cowling afterwards. There is also a photo taken of the instrument panel while in cruise before the trouble began.
Comments, advice appreciated.
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Post by stroudj on Apr 11, 2020 19:51:02 GMT
I would check the return line and check valve to the turbo. If it clogs up it will blow oil out of the turbo into the exhaust.
Thanks,
Jim
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Post by buzz on Apr 11, 2020 19:54:03 GMT
I'm wondering if your turbo was dumping oil. Ed Midgley on here had an incident where he made a dead stick landing when his scavenge line blocked up. As I recall he lost almost all of the oil. It is thought to have happened due to Aeroshell Sport 4 Oil not being able to take the heat of the turbo. We had quite a discussion about the pros and cons of the different oils. Do you use Sport 4?
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Post by stroudj on Apr 11, 2020 20:07:20 GMT
The Sport 4 oil is not the cause of the problem. Not allowing the turbo to cool down before shutting down the engine is the problem. I have over 800 hrs on my 914 with no issues.
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Post by podpilot on Apr 11, 2020 22:14:23 GMT
I do use sport 4 oil. I am the owner and only pilot of the aircraft. I have always followed the cool down protocol for the turbo.
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Post by buzz on Apr 12, 2020 0:19:54 GMT
The Sport 4 oil is not the cause of the problem. Not allowing the turbo to cool down before shutting down the engine is the problem. I have over 800 hrs on my 914 with no issues. Ok that's good. I don't remember the cool down coming up in the last discussion. Only that the oil was a question. But if that's the fix then that's great. I never could figure out exactly why using the recommended oil should result in an engine failure. |
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Post by buzz on Apr 12, 2020 0:26:09 GMT
I do use sport 4 oil. I am the owner and only pilot of the aircraft. I have always followed the cool down protocol for the turbo. To be honest this is the first time I had heard that improper cool down was the cause. |
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Post by buzz on Apr 12, 2020 0:28:11 GMT
The Sport 4 oil is not the cause of the problem. Not allowing the turbo to cool down before shutting down the engine is the problem. I have over 800 hrs on my 914 with no issues. Not doubting you at all but just curious about the source of the information. Is this from Rotax? |
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Post by stroudj on Apr 12, 2020 1:29:38 GMT
It’s taught at the Rotax Service & Maintence class at Lockwood. Most of the time during the turbo cools off during the landing process and no additional cooling is required.
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Post by buzz on Apr 12, 2020 1:45:03 GMT
It’s taught at the Rotax Service & Maintence class at Lockwood. Most of the time during the turbo cools off during the landing process and no additional cooling is required. Well that's a purty good source of info. I know a lot of people say the taxi back to the hanger is usually sufficient to cool but I always do the 1 minute cool at 2500 after I get to the hangar. |
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Post by LSA Flyer on Apr 12, 2020 2:05:35 GMT
First of all, glad you were able to land safely.
Question: Was the oil tank down to only about a pint? I assume the tank was confirmed full after the oil change. If you lost that much oil with visible smoke but no spike in oil temp, it's got to be blowing past the internal oil seal in the turbo. The prior suggestion to look for blockage in the return line and check valve sounds like a smart place to start. You should also pull some spark plugs to look for oil fouling evidence.
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Post by podpilot on Apr 12, 2020 21:51:55 GMT
The plane remains in a maintenance shop at ATW. I should get some information this week. Tecnam USA in Florida has been notified.
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Post by Ed Midgley on Apr 12, 2020 23:05:52 GMT
That’s about all the oil I had left after the same thing happened. You will probably see little black flakes in the oil sump caused from coked oil.
I’ll repeat what may Rotax School instructor said “Shell and Rotax both recommend Sport 4 oil but, it will coke up turbo’s and cause problems. Use Mobil 1 4T motorcycle racing oil”
You will have to change oil more often but it’s worth the peace of mind.
From the time you enter the pattern until you get to your hangar the turbo is cooling.
We were both lucky in being able to land ASAP. My engine got down to 6psi on the decent with the engine windmilling as I had shut it off.
I have almost 200hrs since the event with no problems.
I cruise at 35”MAP so my turbo probably runs hotter than someone running 30” or less.
Ed
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Post by Ed Midgley on Apr 12, 2020 23:24:00 GMT
Podpilot I sent you a PM
Ed
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Post by podpilot on Apr 17, 2020 16:25:07 GMT
Update: Initial reports from mechanic: No metal in filter or scavenger pump. There were flakes of what appear to be brass in oil sump on bottom of turbo likely from bearing. Turbo blades, exhaust side were bent. Abnormal play found in turbo shaft. One supporting bracket for turbo was cracked indicating vibration prior to failure. No evidence of oil "coking". Oil analysis, bore scope pending. Link to photos is shown below. Any advice comments or reports of anything similar are welcome. www.dropbox.com/sh/wmrghn7hcl1soqq/AAD4-QWE9vev5zNPsGa8cw8pa?dl=0 |
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